The present invention relates to a deep-drilling tool including a tube provided with an internal passage or channel, and a drill head attached to one end of the tube.
Deep-drilling tools of this general type are known. When drilling begins, they are guided by a guide sleeve pressed against an end face of the workpiece to be drilled, the guide sleeve being thereby concentrically placed relative to the hole to be drilled in the workpiece. Two known methods of deep drilling are the so-called BTA-method and the single-lip drilling method. In both, the drilling tool has a passage or channel defined in its interior.
In the BTA-method, cooling of the drill head and simultaneous removal of the chips generated are effected by a soluble cutting or lubricating oil (cooling lubricant) which is pressure-fed into the hole or bore being drilled at the outside, along the circumference of the tube carrying the drill head; the lubricating oil being removed through the interior passage of the tool, carrying the chips away with it. The supply of lubricating oil is effected by a lubricating-oil supply device (hereinafter referred to as an LOSD), which includes a housing with a cylindrical interior. The lubricating oil is pressure-fed into this housing, and the LOSD is sealed off from both the bore and the drill spindle. The LOSD also serves to support the tube carrying the drill head such that the tube is spaced apart from the bore.
In the single-lip method, the lubricating oil is guided to the drill bit via the internal passage and is removed, together with the chips, along the circumference of the tube carrying the drill head, or in other words inside the space that exists between this tube and the bore.
In order to enable lubricant oil to be pressure-fed into the bore through the space between the circumference of the tube and the bore (the BTA method) or to be carried away out of the bore through that space (the single-lip drilling method), and in order to prevent the tube from pressing against the inner wall of the bore, the drill bits on the drill head have a diameter that is somewhat larger than the diameter of the tube carrying the drill head. As a result, the drill head cannot be retracted through the LOSD when the tool is to be changed. The drill head has to be unscrewed from the tube first. Only then can the tube be pulled out through the LOSD, or through the stuffing box that seals off the tube in the LOSD. In the final analysis, this means that before changing the tool at the tool spindle, the tool comprising the tube and the drill head has to be disassembled.
This is particularly disadvantageous when a fully automatic tool change is desired. To accomplish such a change the entire tool, comprising the tube and the drill head that has been screwed into place as well as an insertion cone mounted on the end of the tube, is engaged by a gripping tool and then changed. However, to do this the entire tool has to be pulled out of the LOSD, or out of the seals (stuffing box) provided in it. This could not be done with tools of the type heretofore known, because as noted above the stuffing box at the end of the LOSD is adapted to the diameter of the tube on the one hand, while on the other hand the diameter of the drill head is somewhat larger than that of the tube.